Application Of Activated Carbon Research Articles

Measuring the bioavailability of polychlorinated biphenyls to earthworms in soil enriched with biochar or activated carbon using triolein-embedded cellulose acetate membrane

Polychlorinated biphenyls (PCBs) are persistent soil contaminants that resist biodegradation and present serious risks to living organisms. The presence of biochar in soils can lower the availability of PCBs to biota. In this study, the effect of biochar enrichment in soils on bioaccumulation of PCBs was investigated. We applied two types of biochar including pine needle biochar (PC) and wheat straw biochar (WC), and an activated carbon (AC) to soil (2 % w/w) and employed two alternative methods to quantified rates of bioaccumulation: a living bioassay (using earthworm, Eisenia fetida, as a model organism) and a triolein-embedded cellulose acetate membrane (TECAM). Our results show that the application of biochar or AC greatly reduced the uptake of PCBs (particularly less-chlorinated PCBs) by earthworms (the reduction in total PCBs concentration was up to 40.0 and 49.0 % for PC and WC treatments, while 71.6 % for AC application). We found that the bioaccumulation factors (BAFs) for PCBs in the earthworms in biochar/AC-enriched soils were strongly correlated with O:C ratio of the biochar/AC (R 2 = 0.998, p < 0.05). We observed that BAFs increased at log K OW below 6.3 and decreased at log K OW values greater than 6.3. We demonstrated that the concentration of PCBs in TECAM membranes were positively correlated with the concentration of PCBs earthworms in soil. TECAM offers an efficient and cost-effective method for predicting the bioavailability of PCBs in field-contaminated soils undergoing sorbent-based remediation.

Adsorption and removal of tetracycline from water by petroleum coke-derived highly porous activated carbon

Herein, petroleum coke (PC) derived activated carbons (ACs) were prepared via KOH activation process. The as-prepared ACs exhibited a large surface area (2800–2900m2/g) and total pore volume (1.4–2.1cm3/g). In addition, the oxygen-correlated functional groups endow the resultant ACs with an acid surface. Combining the structural characters with the surface properties, these ACs were successfully applied for the effective removal of a commonly-used antibiotics (tetracycline) from drinking water for the first time. As a typical example, the maximum adsorption capacities of 897.6, 961.5 and 1121.5mg/g were obtained at the temperature of 303, 313 and 323K, respectively, for tetracycline removal, which was higher than that of other reports. Furthermore, the adsorption parameters, including the initial concentration, contact time, pH of solution, ionic strength and temperature, were investigated. The adsorption isotherms and kinetics were also discussed in detail. It was observed that the adsorption isotherms were well fitted to Freundlich model, the kinetics studies implied the adsorption process was attributed to pseudo-second-order model. The above-mentioned results proved the successful application of the as-synthesized ACs for effective removal of tetracycline.

Surfactant removal from aqueous solutions onto activated carbon using UV spectroscopy

The anionic surfactant sodium dodecyl sulfate (SDS or NaDS) was adsorbed from aqueous solutions onto four different sizes of activated carbons (ACs). The concentrations of anionic surfactant in aqueous solutions were determined by UV spectroscopy. In this work, anionic surfactant had a linear dependence of UV absorbance on the surfactant concentration at 200 nm. Changes in the textural properties of the AC after adsorption of surfactants will be studied by adsorption and mercury intrusion porosimetry, and could be correlated to surface characteristics and adsorptive capacity. The mechanism of adsorption was found to be simple. At low surfactant concentrations, adsorption occurred in micropores. We concluded that this surfactant is adsorbed as individual molecules. Adsorption from more concentrated solutions probably occurs in meso and macropores, and resembles surfactant adsorption on flat carbon surfaces. ACs with small pores appears to be most effective for surfactant removal. Controlling the pore size distribution of the ACs would be beneficial in the application of ACs for removal of surfactants from wastewater.

Optimization of preparation conditions of activated carbon from agriculture waste utilizing factorial design

In this work, activated carbon (AC) was prepared from rice husk by chemical activation. AC was prepared using factorial design as a statistical tool to facilitate the process and to reach results that would not be possible changing one variable at a time. AC characterizations were performed by N2 adsorption/desorption and surface group titulation. Some AC was obtained with high surface area, up to 1593m2g−1, high mesopore volume, up to 1.22cm3g−1, and surface acids, up to 4.4mmolg−1. These characteristics are very important for AC application such as adsorption or acid catalysis. With this work, we were able to conclude that it is possible to prepare activated carbon from rice husk with high surface area, mesoporosity and surface acid groups, using factorial design as an efficient tool to plan the experiments.

Effect of biochars, activated carbon and multiwalled carbon nanotubes on phytotoxicity of sediment contaminated by inorganic and organic pollutants

To reduce the risk related with the presence of contaminants in sediments, methods based on the use of adsorbents (mainly activated carbon) are applied. Adsorbents neutralise the contaminants by reducing their mobility, bioavailability and toxicity. The objective of this study was to determine the toxicity of sediment contaminated with organic compounds and heavy metals with and without the addition of selected adsorbents. In the study three carbonaceous materials (CM) potentially useful in remediation were applied: activated carbon (AC), biochars (BC1, BC2), and multi-walled carbon nanotubes (CNTs). The effect of the dose, particle diameter and time of contact between sediment and CM on the effectiveness of the detoxification were estimated. Ecotoxicological assessment was made based on the Phytotoxkit F™ test, using Lepidium sativum as the test plant. The materials tested reduced the negative effect of sediment on L. sativum. The highest effectiveness was achieved after the application of AC (70% reduction of seed germination inhibition, 27.5% reduction of root growth inhibition). The reduction of phytotoxicity of the sediment as a result of addition of BC1, BC2 and CNT varied within the range from 30 to 40% (reduction of seed germination inhibition) and from 17.7 to 28.9% (reduction of root growth inhibition). The reduction of sediment toxicity decreased with decreasing diameter of the biochars applied. Probably because of increasing fouling extension of the time of contact between CM and sediment had an unfavourable effect on the reduction of root growth inhibition in the case of all materials tested.

Application of corncob-based activated carbon as electrode material for electric double-layer capacitors

To investigate the influence of expansion pretreatment for materials on carbon structure, activated carbons (ACs) were prepared from corncob with/without expansion pretreatment by KOH activation, the structure properties of which were determined based on N2 adsorption isotherm at 77 K. The results show that the expansion pretreatment for corncobs is beneficial to the preparation of ACs with high surface area. The specific surface area of the AC derived from corncob with expansion pretreatment (AC-1) is 32.5% larger than that without expansion pretreatment (AC-2). Furthermore, to probe the potential application of corncob-based ACs in electric double-layer capacitor (EDLC), the prepared ACs were used as electrode materials to assemble EDLC, and its electrochemical performance was investigated. The results indicate that the specific capacitance of AC-1 is 276 F/g at 50 mA/g, which increases by 27% compared with that of AC-2 (217 F/g). As electrode materials, AC-1 presents a better electrochemical performance than AC-2, including a higher voltage maintenance ratio and a lower leakage current.

Feasibility study on reducing lead and cadmium absorption by spinach (Spinacia oleracea L.) in a contaminated soil using nanoporous activated carbon

Activated carbons (AC) have been long recognized as prominent absorbents in industries and feature numerous applications in preventing or absorbing the harmful gases and liquids and could be employed for filtration and remediation or even reutilization of chemicals. In order to investigate the capacity of AC in reducing the absorption of heavy metals (HM) including lead (Pb) and cadmium (Cd) and dual complex (Pb × Cd) by spinach, a factorial experiment in a completely randomized design with three replications on a pot trial was conducted. Three factors including five levels of AC 0, 5000, 10000, 15000, 20000 mg/kg soil, one concentration level of Pb 4,000 mg/kg soil and one concentration level of cadmium Cd 8 mg/kg soil were tested. The index of heavy metal concentration was calculated in leaf, stem and root and their corresponding dry weights. Results illustrated that in contaminated soils, plants with AC exhibited a superior reduction of absorption of HM vis-a-vis the plants without AC. The foremost result regarding the impact of AC on reducing the concentration of Pb and Cd was observed in 20,000 level of AC. This reveals that AC declined the soil contamination and lessened the accumulation of HM into the shoots and roots. Results suggest that the application of AC may be an eligible solution for decreasing the translocation of HM into the plants.

Ecotoxicological Effects of Activated Carbon Amendments on Macroinvertebrates in Nonpolluted and Polluted Sediments

Amendment of contaminated sediment with activated carbon (AC) is a remediation technique that has demonstrated its ability to reduce aqueous concentrations of hydrophobic organic compounds. The application of AC, however, requires information on possible ecological effects, especially effects on benthic species. Here, we provide data on the effects of AC addition on locomotion, ventilation, sediment avoidance, mortality, and growth of two benthic species, Gammarus pulex and Asellus aquaticus , in clean versus polycyclic aromatic hydrocarbon (PAH) contaminated sediment. Exposure to PAH was quantified using 76 μm polyoxymethylene passive samplers. In clean sediment, AC amendment caused no behavioral effects on both species after 3-5 days exposure, no effect on the survival of A. aquaticus , moderate effect on the survival of G. pulex (LC(50) = 3.1% AC), and no effects on growth. In contrast, no survivors were detected in PAH contaminated sediment without AC. Addition of 1% AC, however, resulted in a substantial reduction of water exposure concentration and increased survival of G. pulex and A. aquaticus by 30 and 100% in 8 days and 5 and 50% after 28 days exposure, respectively. We conclude that AC addition leads to substantial improvement of habitat quality in contaminated sediments and outweighs ecological side effects.

Field Application of Activated Carbon Amendment for In-Situ Stabilization of Polychlorinated Biphenyls in Marine Sediment

We report results on the first field-scale application of activated carbon (AC) amendment to contaminated sediment for in-situ stabilization of polychlorinated biphenyls (PCBs). The test was performed on a tidal mud flat at South Basin, adjacent to the former Hunters Point Naval Shipyard, San Francisco Bay, CA. The major goals of the field study were to (1) assess scale up of the AC mixing technology using two available, large-scale devices, (2) validate the effectiveness of the AC amendment at the field scale, and (3) identify possible adverse effects of the remediation technology. Also, the test allowed comparison among monitoring tools, evaluation of longer-term effectiveness of AC amendment, and identification of field-related factors that confound the performance of in-situ biological assessments. Following background pretreatment measurements, we successfully incorporated AC into sediment to a nominal 30 cm depth during a single mixing event, as confirmed by total organic carbon and black carbon contents in the designated test plots. The measured AC dose averaged 2.0-3.2 wt% and varied depending on sampling locations and mixing equipment. AC amendment did not impact sediment resuspension or PCB release into the water column over the treatment plots, nor adversely impactthe existing macro benthic community composition, richness, or diversity. The PCB bioaccumulation in marine clams was reduced when exposed to sediment treated with 2% AC in comparison to the control plot Field-deployed semi permeable membrane devices and polyethylene devices showed about 50% reduction in PCB uptake in AC-treated sediment and similar reduction in estimated pore-water PCB concentration. This reduction was evident even after 13-month post-treatment with then 7 months of continuous exposure, indicating AC treatment efficacy was retained for an extended period. Aqueous equilibrium PCB concentrations and PCB desorption showed an AC-dose response. Field-exposed AC after 18 months retained a strong stabilization capability to reduce aqueous equilibrium PCB concentrations by about 90%, which also supports the long-term effectiveness of AC in the field. Additional mixing during or after AC deployment, increasing AC dose, reducing AC-particle size, and sequential deployment of AC dose will likely improve AC-sediment contact and overall effectiveness. The reductions in PCB availability observed with slow mass transfer under field conditions calls for predictive models to assess the long-term trends in pore-water PCB concentrations and the benefits of alternative in-situ AC application and mixing strategies.

Minimum feeding rate of activated carbon to control dioxin emissions from a large-scale municipal solid waste incinerator

To obtain a minimum feeding rate ( F min) of activated carbon (AC), a series of measurements on dioxin emission concentration were carried out in a large-scale municipal solid waste incinerator. It was found that dioxin removal efficiency ( η) increased with an increase in AC feeding concentration. This had an almost linear function to F/ Q when F/ Q was less than 65 mg/Nm 3, where F was the AC feeding rate (mg/min), and Q was the volumetric flow rate of flue gas (Nm 3/min). However, it did not seem to be affected by F/ Q, when F/ Q was larger than 150 mg/Nm 3. On the basis of the experimental data obtained in this study, the removal efficiency of dioxins by the application of AC could be correlated as η (%) = 100/[1.0 + (40.2/( F/ Q) 3)]. It is valid in appropriate conditions ( F/ Q = 10–300 mg/Nm 3) suggested by the study with a statistical error of ±18%. The correlation would be applied to estimate the dioxin removal efficiency ( η) using the F/ Q value. For engineering applications, the ( F/ Q) min could be solved using a graphic illustration method, by which the minimum feeding rate ( F) was obtained if the flue gas volumetric flow rate ( Q) was known.

Modeling Polychlorinated Biphenyl Mass Transfer after Amendment of Contaminated Sediment with Activated Carbon

The sorption kinetics and concentration of polychlorinated biphenyls (PCBs) in historically polluted sediment is modeled to assess a remediation strategy based on in situ PCB sequestration by mixing with activated carbon (AC). We extend our evaluation of a model based on intraparticle diffusion by including a biomimetic semipermeable membrane device (SPMD) and a first-order degradation rate for the aqueous phase. The model predictions are compared with the previously reported experimental PCB concentrations in the bulk water phase and in SPMDs. The simulated scenarios comprise a marine and a freshwater sediment, four PCB congeners, two AC grain sizes, four doses of AC, and comparison with laboratory experiments for up to 540 days of AC amendment slowly mixed with sediment. The model qualitatively reproduces the observed shifts in the PCB distribution during repartitioning after AC amendment but systematically overestimates the overall effect of the treatment in reducing aqueous and SPMD concentrations of PCBs by a factor of 2-6. For our AC application in sediment, competitive sorption of the various solutes apparently requires a reduction by a factor of 16 of the literature values for the AC-water partitioning coefficient measured in pure aqueous systems. With this correction, model results and measurements agree within a factor of 3. We also discuss the impact of the nonlinearity of the AC sorption isotherm and first-order degradation in the aqueous phase. Regular mixing of the sediment accelerates the benefit of the proposed amendment substantially. But according to our scenario, after AC amendment is homogeneously mixed into the sediment and then left undisturbed, aqueous PCB concentrations tend toward the same reduction after approximately 5 or more years.